Competition of Dimerization and Charge Ordering in the Spin-Peierls State of Organic Conductors

TL;DR

This paper investigates how charge ordering influences the spin-Peierls state in organic conductors using a Peierls-Hubbard model, revealing a phase transition driven by the competition between dimerization and charge ordering.

Contribution

It introduces a variational approach combined with renormalization group analysis to study the interplay of charge ordering and dimerization in a quarter-filled Peierls-Hubbard model.

Findings

Charge ordering appears at a critical interaction V_c.

Bond distortion peaks at V_c due to competition.

A second-order phase transition occurs at V_c.

Abstract

The effect of the charge ordering on the spin-Peierls (SP) state has been examined by using a Peierls-Hubbard model at quarter-filling with dimerization, on-site and nearest-neighbor repulsive interactions. By taking account of the presence of dimerization, a bond distortion is calculated variationally with the renormalization group method based on bosonization. When the charge ordering appears at V=V_c with increasing the nearest-neighbor interaction (V), the distortion exhibits a maximum due to competition between the dimerization and the charge ordering. It is shown that the second-order phase transition occurs from the SP state with the bond alternation to a mixed state with an additional component of the site alternationat V = V_c.